Waterflooding is a commonly employed method for recovering additional amounts of petroleum beyond the amount recoverable by primary means, and comprises injecting field water into the formation to displace petroleum through the formation to the production well. Water does not displace petroleum efficiently, however, since oil and water are immiscible and the interfacial tension between water and oil is quite high. After completion of primary and secondary recovery, it is common to find that from 50 to 70 percent of the oil originally present in the formation still remains unrecovered in the formation.
It is recognized in the prior art that waterflooding can only recover a fraction of the oil present in the formation and there are many prior art references suggesting incorporating surface active agents or surfactants in the flood water for the purpose of reducing the interfacial tension between the injected water and the formation petroleum, which accomplishes recovery of a greater portion of the residual oil after primary production than is possible with water flooding. Many surfactants have been disclosed in many references for use in oil recovery operations, but many of these are limited with respect to formation water salinity, hardness and other factors which greatly reduce their applicability. Thus, it can be readily appreciated that there is a significant commercial need for an oil recovery method which can be applied to formations containing high salinity and hard water.
Accordingly, an object of this invention is to provide an improved process for the recovery of oil from subterranean oil-bearing formations.
Another object of this invention is to provide a process for the recovery of oil from subterranean oil-bearing formations which exhibits improved oil recovery efficiency.
Another object of this invention is to provide a surfactant system which is effective for post-primary oil recovery.
A further object of this invention is to provide a surfactant system for the recovery of oil from subterranean oil-bearing formations which is economical in operation and uncomplicated in execution.
Other aspects, objects and advantages of the invention will become readily apparent to those skilled in the art from a reading of the following detailed description of the invention and the appended claims.